In act 1 of the play, Betty lies incapacitated on her bed and refuses to respond to her father's questions and demands. The previous night, Betty's father, Reverend Parris, caught Betty and several other girls dancing in the woods, which is a serious offense in Salem's austere, religious community. Betty is only ten years old and is overwhelmed with fear and anxiety. She is extremely worried about the repercussions of dancing in the woods and is essentially paralyzed with fear. The first time Betty screams is when she is alone in the room with Abigail. She attempts to jump out of the window and screams hysterically before she confronts Abigail about drinking the blood. However, Abigail strikes Betty and threatens to kill her if she does not corroborate her story. Whenever the adults reenter Betty's room, she stops screaming and becomes silent.

After Abigail begins accusing innocent citizens of being involved in witchcraft, Betty realizes that there is a way to avoid punishment, so she screams,

I saw George Jacobs with the Devil! I saw Goody Howe with the Devil!

She then proceeds to accuse several other citizens of being involved in witchcraft before the curtain falls. Overall, Betty initially screams because she is overwhelmed with emotions and is afraid of being punished for dancing in the woods. Towards the end of act 1, Betty screams as she accuses innocent citizens of witchcraft in order to avoid punishment.

The whole reason for the Salem witch trials, at least as portrayed in Arthur Miller's The Crucible, is that some young girls were in the forest dancing and dabbling in some witchcraft-like behaviors and were seen by the Reverend Parris. Because they are afraid of being punished, probably by a humiliating and painful public whipping, the girls begin an elaborate farce which the adults around them are all too willing to believe.

Betty is one of those girls; even worse, her father is the one who caught them in the forest last night. This morning she is lying on her bed and does not (will not) move despite all of the commotion and attention which is centered around her. 

Betty screams several times in act one of this play. The first time is when she is alone with the girls and Abigail frightens and practically beats Betty into responding to her demands. Betty first tries to jump out the window and then she starts rather hysterically accusing Abigail of doing worse things than the rest of them did last night. After Abigail hits her again, Betty is more subdued. Clearly Betty is terrified about what her father would do if he knew the truth about last night's activities, but she is also terrified by her cousin, Abigail.

At the end of the act, Betty cries out again; this time she does so with relief because she sees that Abigail has found a way for all of the girls to avoid punishment. When Abigail senses that Reverend Hale and her uncle, Parris, are inclined to believe in witchcraft (Hale in earnest, Paris to avoid bringing trouble into his house), she begins the charade and the other girls follow. Betty joins the throng of voices:

Betty, calling out hysterically and with great relief: I saw Martha Bellows with the Devil!

Betty does not say much in this act; when she does speak it is often a kind of screaming out of fear from either Abigail or her father.